1. Field of the Invention
With reference to the classification of art as established in the U.S. Patent and Trademark Office the present invention is found in the general Class entitled, "Turning" (class 82) and more particularly in the subclass thereunder entitled, "centers" (subclass 33).
2. Description of the Prior Art
Live centers are well known in the field of turning and in particular the use of ball bearings in live centers. When live centers are used the hardened center is free turning in bearings. As reduced to practice, these bearings are protected by a grease seal or shield. A grease seal has the lip portion in sliding contact with the movable center member and this sliding contact has a tendency to wear both the flexible lip of the seal and the hardened center member. In the case of centers as shown in prior art devices where the grease seal is not protected, the grit from grinding as carried by the flushing lubricant normally used in the turning or grinding operation has a tendency to combine with the lip of the grease seal device to increase the abrasive action on the revolving center portion. When this occurs not only does the grease seal have to be replaced but after two or three replacements the revolving center portion must also be replaced in order to provide a smooth surface or land for the lip to ride. When and where the center is a hardened ground piece of steel this replacement is usually rather expensive. On many occasions before the damage to the live center has been detected a contamination of the bearings causes excessive wear of the bearings. The present invention proposes to protect the lip of the grease seal or shield and at the same time provide a renewal surface which can be replaced when the flexible lip of the grease shield is excessively worn.